Optimization of process parameters of CO₂ laser beam butt joints of SS321

This paper identifies the critical process parameters affecting distortion and residual stresses in laser-welded structures, specifically focusing on CO2 laser beam butt welding of SS321 stainless steel alloys. An experimental methodology employing an L4 orthogonal array was utilized, and ANOVA was applied to statistically determine the most influential factors. Non-destructive X-ray diffraction methods were used to measure lattice dimensions and analyze residual stresses on the upper surface of the welded plates. The findings indicate that welding speed contributes 55% to distortion and 36% to residual stresses, while laser power contributes 38% to distortion and 27% to residual stresses. The residual stresses ranged from 108 to 179 MPa, and distortions ranged from 1.18 to 1.94 MPa under welding powers of 3 to 3.5 kV and welding speeds of 1.5 to 1 mm/sec, respectively. Higher heat input led to increased residual stress and distortion. The most effective combination for minimizing distortion and residual stresses was identified as welding speed at level 2 and laser power at level 1. This combination resulted in minimal distortion and compressive residual stresses within the yield limits of the base material. The welds exhibited full penetration and a consistent “Y” shape across all samples, indicating good structural integrity without internal defects. These findings underscore the importance of optimizing welding parameters, particularly welding speed and laser power, to enhance the quality and performance of laser-welded SS321 joints.